Multi Regime combustion under technically relevant conditions: Experimental and numerical investigation of thermo-chemical states and flame structures

湍流燃烧可分为预混燃烧和非预混燃烧。这两种极限情况已被广泛研究，并已开发出预混和非预混火焰的数学模型。除了这两个限制，分层和部分预混火焰也进行了研究，然而，使用预混或非预混模型。火焰既不能被归类为预混的，也不能被归类为非预混的（多区域燃烧），火焰的建模是一个开放的科学问题。多区燃烧广泛存在于燃气轮机或发动机等实际系统中，最近的研究表明，多区燃烧的局部火焰结构与两种极限情况有很大的不同。目前，没有合适的LES模型存在，是能够描述的预混/非预混的限制，以及中间状态。此外，没有实验参考数据集，其中不同的火焰结构是通过边界条件的系统变化来实现的。因此，本研究的目的是对多工况燃烧进行系统的实验和数值研究，模型开发和分析。在实验工作包AP 1中，将开发具有用于生成参考数据的明确边界条件的燃烧器。火焰稳定是通过再循环区实现的，这样，燃烧状态可以通过改变速度和化学计量的入口条件来控制。冷流场和混合流场将采用高速PIV和拉曼光谱进行表征。对于燃烧的情况下，热化学状态将记录与拉曼/瑞利散射。此外，同时定量OH-LIF测量将首次进行。在数值AP 2二维火焰方程（混合分数和进展变量配方）将被解决。对于随后的使用LES和实验的比较，一种新的参数化将开发基于额外的进展变量，而不是标量耗散率。最初，该模型将测试完全解决方案的三重火焰。对于LES小火焰表，将分析和整合来自实验确定的联合概率密度函数的统计信息。在AP 3中，将结合实验和数值方法。作为第一步，将验证LES的结果。随后，将进行燃烧状态的识别、局部热化学状态和火焰结构的表征。该分析将基于本项目开发的一种新的无梯度火焰识别和火焰表征方法。该项目将与作为墨卡托研究员的Vervisch教授密切合作进行。

Turbulent combustion can be classified as premixed or non-premixed. These two limiting cases have been studied extensively and mathematical models have been developed for premixed and non-premixed flames. Besides these two limits, stratified and partially premixed flames have also been investigated, using however either premixed or non-premixed models. Modeling of flames, which can neither be categorized as premixed nor as non-premixed (multi regime combustion), is an open scientific issue. Multi regime combustion can be found in a variety of practical systems such as gas turbines or engines.Recent studies have shown that the local flame structures in multi regime combustion can differ significantly from both limiting cases. Currently, no suitable LES model exists that is capable of describing both the premixed/non-premixed limits as well as the intermediate states. Furthermore, no experimental reference data set is available, where the different flame structures are realized through systematic variations of boundary conditions. Therefore, the objective of this study is a systematic experimental and numerical investigation, model development and analysis of multi regime combustion.The research project consists of 3 work packages (AP). In the experimental work package AP1 a burner with well-defined boundary conditions for generating the reference data will be developed. Flame stabilization is achieved through recirculation zones such that the combustion regime can be controlled by varying the inlet conditions both in velocity and stoichiometry. The cold flow and mixture field will be characterized with high-speed PIV and Raman spectroscopy. For the combusting cases, the thermo-chemical state will be recorded with Raman/Rayleigh scattering. Furthermore, simultaneous quantitative OH-LIF measurements will be carried out for the first time.In the numerical AP2 two-dimensional flamelet equations (mixture fraction and progress variable formulation) will be solved. For a subsequent usage in LES and for comparison with the experiments a novel parameterization will be developed based on additional progress variables instead of scalar dissipation rates. Initially, the model will be tested against fully resolved solutions of a triple flame. For the LES flamelet tables, statistical information from experimentally determined joint probability density functions will be analyzed and integrated.In AP3 experimental and numerical methods will be combined. As a first step the results from the LES will be validated. Subsequently, the identification of combustion regimes, the characterization of the local thermo-chemical state and the flame structure will be carried out. This analysis will be based on a novel gradient-free flame identification and flame characterization method developed in this project. The project will be carried out in close collaboration with Prof. Vervisch as Mercator fellow.